Electrochemical Investigation of Hydroxy-Substituted Thiosemicarbazone Derivatives as an Effective Corrosion Inhibitor for Mild Steel

This study provides a comparative investigation of 3,4-dihydroxybenzaldehyde thiosemicarbazone (CIn1) and 2,3,4-trihydroxybenzaldehyde thiosemicarbazone (CIn2) in both acidic (0.1 M and 1 M HCl) and marine (3.5% NaCl) environments on mild steel, which has not been extensively explored, through electrochemical impedance spectroscopy, potentiodynamic polarization studies, and weight loss analysis at different temperatures and concentration. The density functional theory indicates that CIn1 has higher electron-donating ability than CIn2, which correlates with their inhibition efficiency. Molecular dynamics simulations were used to investigate the adsorption characteristics of the CIn1 and CIn2 molecules on a modeled Fe (110) surface in an aqueous environment, providing insights at the molecular scale, which indicates that CIn1 has stronger adsorption energy than CIn2, leading to better surface coverage and protection. The experimental and theoretical findings demonstrated that synthesized hydroxy-substituted thiosemicarbazone derivatives have shown promise in protecting MS surfaces from corrosion in acidic and marine environments. From the results, CIn1 exhibited maximum %eta PDP: 95.38% for 0.1 M HCl, 95.26% for 1 M HCl, and 78.37% for 3.5% NaCl solution, and CIn2 exhibited maximum %eta PDP : 92.29% for 0.1 M HCl, 96.60% for 1 M HCl, and 59.76% for 3.5% NaCl solution.